The present invention uniquely combines radiant infrared and convective heat transfer functions in a single device.
The general method of transferring energy by radiant means relates to the type of heaters or burners disclosed in U.S. Pat. Nos. 3,824,064; 4,189,297; 4,255,123; 4,272,237; and 4,290,746. Those burners were all designed to combust a gas/air mixture by blowing it through a porous, fibrous, refractory matrix and combusting it at or slightly within the outer surface of the matrix. The resultant combustion in the presence of large numbers of tiny refractory fibers converts a relatively large proportion of the heat of combustion to electromagnetic energy, much of which radiates outwardly toward the target(s) to be heated. Typically, the temperature achieved at the burning face of the matrix is between 1,150.degree. F. and 1,650.degree. F.
The above technology is well known, and such gas-fired, matrix-type heaters are able to achieve "conversion-to-radiation" efficiencies of 40% to 60%. Various patented and non-patented techniques are used to secure the refractory matrix to or within the gas/air mixture plenum and to constrict or otherwise control the combustion occurring at the outer face of the matrix. None of the known gas-fired, matrix-type heaters have been designed to utilize the 40% to 60% of the total combustion hat value which is contained in the gaseous products of combustion, in the immediate heat process zone or area. Rather, that heat is typically permitted to escape from the immediate process area in controlled, or sometimes uncontrolled fashion as exhaust.
In certain instances, the gaseous products of combustion from the above type of heaters may be exhausted after being drawn through a target web which is of sufficient porosity and in a moisture level condition or of a composition which permits such draw-through without damaging the web. These instances are exceptions rather than being commonplace, and the combustion product gases are not purposely controlled prior to contact with the web or other target(s) to be heated. In fact, flow-through heating of porous webs is not a recent technological development and has been used in various process systems for more than 30 years.
Although the gas-fired, matrix-type heater represented a significant advance in radiant heat transfer technology, those heating or burner devices have not, by themselves, been designed to effect both radiant and convective heat transfer nor have they been designed to provide mass transfer of water or solvent vapors from targets in those process applications in which the objective is the removal of liquids from the target. To accomplish these functions has in the past required that these burners or heaters be used in combination with other, sometimes patented devices such as air foils and exhaust assemblies.